The present technology relates to a solid-state imaging device and an electronic apparatus including the solid-state imaging device.
There is a CMOS (Complementary Metal Oxide Semiconductor) solid-state imaging device as one solid-state imaging device which is used in electronic apparatuses such as digital still cameras, digital video cameras, or the like.
The CMOS solid-state imaging device includes a semiconductor substrate which is formed of silicon, or the like, and includes a pixel region in which a plurality of pixels is arranged, for example, in a matrix shape, on the semiconductor substrate. Each pixel which is arranged in the pixel region is configured by a photodiode as a light receiving element having a photoelectric conversion function, and a plurality of MOS transistors.
In the CMOS solid-state imaging device, a wiring layer in which, for example, a plurality of wirings is laminated inter layers through an insulating film is provided on one plate surface of the semiconductor substrate. In addition, the CMOS solid-state imaging device has a color filter layer, and a plurality of micro lenses on the side where the semiconductor substrate is irradiated with light.
The color filter layer is divided into a plurality of color filters for each photodiode which configures each of the pixels. Each of the color filters is a filter portion of any color of, for example, red, green, and blue, and transmits light of each color component. A micro lens is formed for each pixel, corresponding to the photodiode configuring each pixel. The micro lens condenses the input light from the outside to a photodiode of corresponding pixel.
For the CMOS solid-state imaging device with the above described configuration, there are a so-called front side illumination type and a backside illumination type. The front side illumination and the backside illumination are different from each other, since the input side of light with respect to the semiconductor substrate having the wiring layer on one plate surface side is the front side for the front side illumination, and the rear side for the backside illumination.
Specifically, in the front side illumination CMOS solid-state imaging device, the color filter layer and the micro lens are formed through the wiring layer which is provided on one side of the semiconductor substrate with respect to the semiconductor substrate. That is, in the structure of the front side illumination, the wiring layer is provided on the side where the light is input with respect to the semiconductor substrate.
On the contrary, in the backside illumination CMOS solid-state imaging device, the color filter layer and the micro lens are formed on the side opposite to the side where the wiring layer is provided with respect to the semiconductor substrate. That is, in the structure of the backside illumination, the wiring layer is provided on the side opposite to the side where the light is input with respect to the semiconductor substrate.
Due to the above described difference in the structure of the front side illumination and the backside illumination, there are operational differences between both as follows. In a case of the front side illumination, the light which is input from the micro lens side transmits the color filter layer, passes through the inside of the wiring layer, and then is received by the photodiode of each pixel which configures the pixel region.
In contrast to this, in a case of the backside illumination, the light which is input from the micro lens side passes through the color filter layer, and is received by the photodiode of the pixel without passing through the wiring layer. For this reason, according to the structure of the backside illumination, since the light which is input from the micro lens side is received by the photodiode of the pixel without being blocked by the wiring layer, it is possible to secure the actual light receiving area of the photodiode widely, and to improve the sensitivity thereof.
However, there is a problem in the Back side illumination CMOS solid-state imaging device as follows, since the wiring layer is not present on the side where the light is input with respect to the semiconductor substrate. First, in the structure of the backside illumination, it is very difficult to suppress optical color mixing completely. Here, the optical color mixing is a phenomenon in which, in a border portion of pixels where pixels with different colors from each other are close to each other, a part of light which is input to the micro lens corresponding to pixels of one color is input to the photodiode of pixels of the other color.
In addition, in the Back side illumination CMOS solid-state imaging device, for example, when a high intensity light source such as the sun or the like is photographed, there may be a magenta colored stripe shaped pixel defect (hereinafter, referred to as “Mg flare”) which is referred to as magenta flare, or the like. The Mg flare occurs as follows.
A part of the light which is input from the micro lens toward the photodiode side of the pixel becomes light which goes toward the micro lens side from the photodiode side as reflected light or diffracted light. The reflected light or the diffracted light passing through the micro lens, or the like, is reflected by seal glass which covers the micro lens, or the like, in the package of the CMOS solid-state imaging device, and is input from the micro lens again toward the photodiode side. The light which is input to the photodiode side again in this manner causes the optical color mixing to uniformly occur in pixels of each color of, for example, red, green, and blue.
In addition, in the CMOS solid-state imaging device, processing, which is referred to as white balance processing, is performed so as to arrange spectral characteristics of light of each color component, in the process of signal processing. According to the white balance processing, for example, when the color filter layers are divided into three color filters of red, green, and blue, the red and blue signals have a larger gain than the green signal, and are emphasized. The Mg flare occurs due to such a white balance processing which is performed in a state where each color pixel is uniformly mixed, as described above.
In order to solve the problem in the above described backside illumination structure, the technology described in Japanese Unexamined Patent Application Publication No. 2010-186818 has been proposed, and has come into practical use. In the technology in Japanese Unexamined Patent Application Publication No. 2010-186818, a light shielding film is formed through an insulating layer in the pixel boundary on the light receiving surface of the photodiode, that is, between the adjacent pixels, in between the semiconductor substrate on which the photodiode is formed and the color filter layer.
The technology in Japanese Unexamined Patent Application Publication No. 2010-186818 is considered to be reliably effective when it comes to suppressing the above described optical color mixing and Mg flare. However, according to the technology in Japanese Unexamined Patent Application Publication No. 2010-186818, the sensitivity may be decreased, since a part of the light to be sensed by the pixel is blocked due to the light shielding film which is formed between the adjacent pixels. The degree of decrease in sensitivity due to the light shielding film which is formed between the adjacent pixels depends on the pixel pitches between the pixels in the CMOS solid-state imaging device, the line width of the light shielding film, a light condensing structure, or the like, however, there is a case where the sensitivity is decreased by about 10% in practice due to the light shielding film.
Therefore, in order to suppress such a decrease in sensitivity due to the light shielding film which is formed between the adjacent pixels, the technology described in Japanese Unexamined Patent Application Publication No. 2010-109295 has been proposed. The technology described in Japanese Unexamined Patent Application Publication No. 2010-109295 focuses on an electrostatic light shielding effect due forming the light shielding film from a metallic material, and forms the light shielding film using a non-conductive material such as amorphous silicon.